1. Field of the Invention
The present invention relates to a power amplifier, and more particularly, to a power amplifier capable of improving the harmonics characteristics of an output signal of an amplifier circuit by correcting a phase of the output signal.
2. Description of the Related Art
Electronic devices employing wireless communications circuits have recently come into widespread since those electronic devices allow for ease of use and mobility and easy setup and maintenance.
Typical examples of electronic devices employing wireless communications circuits may include mobile communications terminals and personal digital assistants.
A wireless communications electronic device uses a transmitter circuit in order to transmit a signal including information.
The transmitter circuit necessarily uses a power amplifier that amplifies the power of a signal to be transmitted.
A signal being output from the power amplifier is subjected to impedance matching and is output through an antenna. Here, the power amplifier is required to have harmonics characteristics of at least −10 dBm or less.
Therefore, in order to remove harmonic components from the output signal, a notch filter used to remove harmonics is provided at an output terminal.
That is, as shown in FIG. 1, a power amplifier 10 according to the related art amplifies balance signals and couples the amplified balance signals to thereby output a single signal, and then removes harmonic components from the output signal through a filter in an output terminal.
However, the balance signals amplified by the power amplifier according to the related art are converted into a single signal while being output. Therefore, unbalanced signal amplification may be caused, thereby deteriorating second harmonic characteristics. Thus, there is a need for power amplifiers capable of improving second harmonic characteristics.